Role of Large-Scale Strike-Slip Faults in the Formation of Petroleum-Bearing Compressional Basin-Mountain Range Systems

Understanding the factors that affect the formation and evolution of petroleum-bearing sedimentary basins plays a critical role in the prospecting and exploitation of oil fields. The formation and evolution of the highly-order coastal and on-land petroleum-bearing Cenozoic basins and their bounding mountain ranges in southern California, USA were initiated and controlled by the San Andreas fault system, a large-scale plate boundary transform fault that separates the Pacific plate from the North American plate. The northeast oblique movement of the Pacific plate relative to the North American plate in conjunction with the big bend of the San Andreas fault in southern California produces intense contractional strain across the Transverse Ranges and leads to the formation of a series of fault and fold structures that shape the salient landscape of southern California. For comparison, we have conducted detailed structural analyses on the basin-mountain range systems in the northern Qinghai-Tibet plateau to discuss the role of the Altyn Tagh fault in (1) development of regional contractional stress field; (2) formation of structures and sedimentary basins; (3) generation of structures that facilitate the migration and capture of oil and gas.Resultsshow that the Altyn Tagh fault has played a similar role in the formation of the spectacular basin-mountain systems to that of the San Andreas fault. The oblique convergence of the Qinghai-Tibet terrane relative to the Tarim basin resulted in the formation of transpressional tectonic regime to the southeastern of the Altyn Tagh fault. Such oblique convergence resulted in a series of strike-slip and thrust faults. As a consequence, the areas from the Kunlun Mountains to the Qilian Mountains form spectacular landforms characterized by alternations of basins and mountain ranges. For both cases of the southern California and the northern Qinghai-Tibet plateau, thrust faulting not only provides a viable mechanism for the migration of oil or gas, but also resulted in fault-propagation folds which serve as the favorable capture structure for oil and gas. One of the key factors that generate such a highly organized petroleum-bearing basin-mountain system is oblique convergence induced slip partitioning which results in the dextral horizontal slip along a major strike slip fault and vertical slip along numerous blind or exposed thrust faults.